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  • 1
    ISSN: 1432-0983
    Keywords: Neurospora ; Tomato ; Nitrate reductase ; Nitrate regulation ; GATA-binding factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nit-2 gene of Neurospora crassa encodes a trans-acting regulatory protein that activates the expression of a number of structural genes which code for nitrogen catabolic enzymes, including nitrate reductase. The NIT2 protein contains a Cys2/Cys2-type zinc-finger DNA-binding domain that recognizes promoter regions of the Neurospora nitrogen-related genes. The NIT2 zincfinger domain/β-Gal fusion protein was shown to recognize and bind in a specific manner to two upstream fragments of the nia gene of Lycopersicon esculentum (tomato) in vitro, whereas two mutant NIT2 proteins failed to bind to the same fragments. The dissociation kinetics of the complexes formed between the NIT2 protein and the Neurospora nit-3 and the tomato nia gene promoters were examined; NIT2 binds more strongly to the nit-3 promoter DNA fragment than it does to fragments derived from the plant nitrate reductase gene itself. The observed specificity of the binding suggests the existence of a NIT2-like homolog which regulates the expression of the nitrate assimilation pathway of higher plants.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A mutant screen was developed to isolate Arabidopsis thaliana mutants affected in the regulation of the nitrate assimilation pathway. A fusion between the tobacco Nii1 gene (that encodes a foliar nitrite reductase involved in nitrate assimilation) and the Gus reporter gene was introduced into A. thaliana, and shown to be properly regulated by nitrate. Moreover, β-glucuronidase (GUS) activity in the transgenic plants was essentially detected in the cotyledons and leaves, showing that the organ-specific expression of the tobacco Nii1 gene was retained in Arabidopsis. M2 plantlets derived from mutagenized seeds homozygous for the Nii-Gus fusion were screened by histochemical staining of whole plates for GUS activity after growth on nitrate or glutamine. About 250 progenies were screened, leading to the isolation of plants showing an enhanced or reduced staining compared to the control non-mutagenized plants. Several mutants were analyzed for the transmission of the phenotype to the M3 generation, as well as for levels of GUS or nitrite reductase activities or mRNA levels. A major problem encountered during the screening was the high background of false positives that reproducibly showed altered GUS histochemical staining compared to control plants and did not, however, display any changes in GUS activity levels. One interesting family of mutants was isolated that overexpressed GUS activity and Nii mRNA in the absence of nitrate. These mutants turned out to be cnx mutants impaired in the molybdenum cofactor biosynthesis that is necessary for nitrate reductase activity. These results may indicate that active nitrate reductase is necessary for a correct regulation of nitrate assimilation genes by nitrate.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5028
    Keywords: budding yeast ; fission yeast ; nitrate reductase ; transcription initiation ; β-galactosidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A fragment comprising 1 kb of the 5′ region and the 81 first nucleotides of the coding region of the tomato nitrate reductase nia gene was placed in translational fusion with the lacZ reporter gene. This construct was introduced in budding and in fission yeast using a derivative of the Saccharomyces cerevisiae/Schizosaccharomyces pombe autonomously replicating vector pUZL. β-galactosidase activity was detected in S. pombe but not in S. cerevisiae. Primer extension experiments show that in fission yeast transcripts are initiated at the same starting point as in tomato, indicating for the first time that a plant promoter can be correctly recognized in fission yeast.
    Type of Medium: Electronic Resource
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